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kk727

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**Question:**The heat capacity of a bomb calorimeter was determined by burning 6.79 g of methane (energy of combustion = -802 kJ/mol CH

_{4}) in the bomb. The temperature changed by 10.8 degrees C.

a. What is the heat capacity of the bomb?

b. A 12.6 g sample of acetylene, C2H2, produced a temperature increase of 16.9 degrees C in the same calorimeter. What is the energy of combustion of acetylene (in kJ/mol) ?

## Homework Equations

I wasn't even sure if there were specific equations to use...I did figure out the problem, but I just did so by logic...kinda.

## The Attempt at a Solution

So for Part A, I first converted the 6.79 g of CH4 to mols, and I got about 0.423 mols. Since I didn't remember if there was a formula for this or not, I kind of just logically figured out to multiply by the -802 kJ/mol, so that mols would cancel out. I then divided by the temperature change, 10.08 degrees C, so that my units would be in kJ/C...which is what heat capacity is measured in.

I ended up getting -31.4 kJ/mol. When I compare this to the answer in my book, it's not supposed to be negative. I can't figure out why.

For Part B, I basically used the same process. I looked at all of the data I had, and saw that I needed to get to kJ/mol. I converted the 12.6 g C2H2 to mols; I got about 0.483 mols. I took my answer from Part A, -31.4 kJ/C, and multiplied by the 16.9 degree temp change to cancel out celcius. I then divided by the mols to get -1098.67 kJ/mol.

So...why are my signs wrong? I believe all of the actual math is right. And is there a specific formula or easy way to do this?

Also, when it says "energy of combustion"...is that E, for energy, or H, for heat? Thanks!